This invention relates generally to container inspection systems, such as glass and plastic containers for the presence of contaminants and hazardous materials. More specifically, this invention relates to a method of identifying uncontaminated containers by detecting the residue of the product originally packaged in the container.
In many industries, including the beverage industry, products are packaged in containers which are returned after use, washed and refilled. Typically refillable containers are made of glass which can be easily cleaned. These containers are washed and then inspected for the presence of foreign matter.
Glass containers have the disadvantages of being fragile and, in the larger volumes, of being relatively heavy. Accordingly, it is highly desirable to use plastic containers because they are less fragile and lighter than glass containers of the same volume. However, plastic materials tend to absorb a variety of organic compounds which may later be desorbed into the product thereby adversely affecting the quality of the product packed in the container. It has been found that the existing methods of inspection are inadequate to detect containers which may have absorbed contaminants.